How Firm a Foundation appeared in Rippon's Selection in 1787, and its author remains unknown. What is known is that the hymn became the unofficial hymn of the American frontier, sung by settlers and circuit riders pushing westward, and it was the hymn sung in the ruins of the Twin Towers on September 14, 2001.
The hymn is built on a series of promises from Scripture, especially Isaiah 43. Each promise is stated as direct speech from God to His people: What more can He say than to you He hath said? God has already spoken. The foundation is already laid. The promises are immutable.
The last verse expands the scope: When through fiery trials thy pathway shall lie, my grace all sufficient shall be thy supply. The original settlers knew fiery trials: disease, starvation, conflict, loss. The hymn promised that God's sufficiency would not fail. Two hundred years later, in the wreckage of terrorism, the hymn proved true again.